Method and apparatus for an OFDMA parallel architecture scheduler

ABSTRACT

A method and apparatus for calculating an optimal sub-channel allocation of Orthogonal Frequency Division Multiple Access (OFDMA) from a first bipartite graph that may map users, to a second bipartite graph that may map additional users, including original users. A calculation of each bipartite graph may include a calculation of maximum weight paths and matchings. Using a bipartite graph method for OFDMA sub-channel allocation may improve the time and complexity when establishing an OFDMA wireless system.

FIELD OF THE INVENTION

The present invention relates to wireless communication, and inparticular to channel allocation management.

BACKGROUND OF THE INVENTION

In Orthogonal Frequency Division Multiple Access (OFDMA) broadbandwireless systems resource blocks may consist of groups of sub-carriers,sub-channels or chunks in frequency. Symbols or groups of symbols may bereferred to as slots or sub-frames in time. OFDMA systems may assign aunique sub-channel to a single user. Sub-channel assignments andmodification of these assignments, including adding and removing users,are typically performed by a sequential algorithm that may be highlycomplex or take a long time to implement.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notlimitation in the figures of the accompanying drawings, in which likereference numerals indicate corresponding, analogous or similarelements, and in which:

FIG. 1 is an exemplary graph illustrating a distribution of OFDMAsignals;

FIGS. 2A and 2B are an exemplary block diagram illustrating connectionsof mobile users to sub-channels;

FIG. 3 is an exemplary block diagram illustrating a connectionarchitecture according to an embodiment of the invention;

FIG. 4 is an exemplary block diagram illustrating connections of anelement according to an embodiment of the invention;

FIG. 5 is an exemplary flowchart illustrating a method in accordancewith an embodiment of the present invention;

FIG. 6 is an exemplary flowchart illustrating a calculation method inaccordance with an embodiment of the present invention; and

FIG. 7 is an exemplary block diagram illustrating connections of a graphin accordance with an embodiment of the present invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of embodiments of theinvention. However, it will be understood by those of ordinary skill inthe art that the embodiments of the invention may be practiced withoutthese specific details. In other instances, well-known methods,procedures, and components have not been described in detail so as notto obscure the present invention.

A data process is here, and generally, considered to be aself-consistent sequence of acts or operations leading to a desiredresult. These include physical manipulations of physical quantities.Usually, though not necessarily, these quantities take the form ofelectrical or magnetic signals capable of being stored, transferred,combined, compared, and otherwise manipulated. It has proven convenientat times, principally for reasons of common usage, to refer to thesesignals as bits, values, elements, symbols, characters, terms, numbersor the like. It should be understood, however, that all of these andsimilar terms are to be associated with the appropriate physicalquantities and are merely convenient labels applied to these quantities.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” or the like, refer to the action and/orprocesses of a computer or computing system, or similar electroniccomputing device, that manipulate and/or transform data represented asphysical, such as electronic, quantities within the computing system'sregisters and/or memories into other data similarly represented asphysical quantities within the computing system's memories, registers orother such information storage, transmission or display devices.

Embodiments of the present invention may include apparatuses forperforming the operations herein. This apparatus may be speciallyconstructed for the desired purposes, or it may comprise a generalpurpose computer selectively activated or reconfigured by a computerprogram stored in the computer. Such a computer program may be stored ina computer readable storage medium, such as, but is not limited to, anytype of disk including floppy disks, optical disks, CD-ROMs,magnetic-optical disks, read-only memories (ROMs), random accessmemories (ROMs), random access memories (RAMs), electricallyprogrammable read-only memories (EPROMs), electrically erasable andprogrammable read only memories (EEPROMs), magnetic or optical cards, orany other type of media suitable for storing electronic instructions,and capable of being coupled to a computer system bus.

The processes and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the desired method. The desired structure for avariety of these systems will appear from the description below. Inaddition, embodiments of the present invention are not described withreference to any particular programming language. It will be appreciatedthat a variety of programming languages may be used to implement theteachings of the invention as described herein.

Unless explicitly stated, the method embodiments described herein arenot constrained to a particular order or sequence. Additionally, some ofthe described method embodiments or elements thereof can occur or beperformed at the same point in time.

FIG. 1 is an exemplary graph illustrating a distribution of signals 100according to an embodiment of the invention. According to an embodimentof the invention, Orthogonal Frequency Division Multiple Access (OFDMA)may be used, and may allow multiple users to communicate simultaneously.Any common protocol that may use OFDMA may be used, for example, ThirdGeneration Partnership Project Long Term Evolution (3GPP LTE), WirelessMetropolitan Area Network (WirelessMAN), or Worldwide Interoperabilityfor Microwave Access (WiMAX), or any other OFDMA protocol. Each user, 1to N, may be assigned a frequency, or sub-channel or chunk, j, and thesesub-channels may be depicted along graph axis 110. Users may communicateinformation fragments or packets, 1 to K, by grouping the informationinto slots or sub-frames, i, and these sub-frames may be depicted alonggraph axis 120. An individual element of data, i, that may correspond toan individual user, j, may be represented by q(i,j) 130. Any otherorganization of data and users 100 that may be used by an OFDMAcommunication protocol are possible possible and within the scope of theinvention.

FIGS. 2A and 2B are block diagrams illustrating connections of users tosub-channels. channels. FIG. 2A is an exemplary block diagram 200illustrating all possible connections of users 205, 210, 215 and 220 tosub-channels 225, 230, 235 and 240 that may be available for an OFDMAcommunication protocol to select from. Prior to application of an OFDMAprotocol any user 205, 210, 215 and 220 may be available to be connectedto any sub-channel 225, 230, 235 and 240. FIG. 2B is an exemplary blockdiagram 250 illustrating a possible set of connections 295 that may beapplied to users 255, 260, 265 and 270 in order to operate an OFDMAcommunication protocol, where each user may be assigned to a uniquesub-channel 275, 280, 285 and 290. The assignment of a user to asub-channel may be performed in order to achieve a highSignal-to-Interference Plus Noise Ratio (SINR).

FIG. 3 is an exemplary block diagram illustrating an OFDMA schedulingdevice 300 according to an embodiment of the invention. By way ofexample, FIG. 3 depicts n available communication sub-channels,sub-channels 331, 332, 333 and up to sub-channel N, 339. It will beunderstood that FIG. 3 depicts an embodiment in which N is 4, but theinvention is not limited in this respect, and any number of sub-channelsN may be used that may be in accordance with any OFDMA communicationprotocol.

Parallel Processing Units (PPU) 321, 322, 323 and up to PPU N 329 may beused for each available communication sub-channel 331, 332, 333 and upto 339, respectively. Each PPU may output communication data to arespective communication sub-channel, for example, PPU 321 may output tosub-channel 331, PPU 322 may output to sub-channel 332 and PPU 323 mayoutput to sub-channel 333, etc. All users may be connected to all PPUs.Thus, user 311 may be connected to all PPUs 321, 322, 323 and up to PPUN 329, and user 312 may likewise be connected to all PPUs 321, 322, 323and up to PPU N 329, etc. Accordingly, any user may be able to utilizeany paired combination of PPU and communication sub-channel.

According to embodiments of the invention, each PPU may be connected toevery other PPU, for example, PPU 321 may be connected to PPU 322, PPU323 and up to PPU N 329; PPU 322 may be connected to PPU 321, 323 and upto PPU N 329, and so on, where each connection may form a bidirectionalcommunication path for exchange of control data as described furtherbelow. It will be noted that in some embodiments there may be twouni-directional paths between the PPU pairs. In another embodiment, thePPUs may each be PPUs may each be connected as spokes to a hub, whichmay receive and/or relay control information among the PPUs. In yetanother embodiment of the invention, the PPUs may be connected in adaisy chain arrangement. It will be noted that other configurations forOFDMA scheduling device 300 are possible and within the scope of theinvention.

In an embodiment of the invention, OFDMA scheduling device 300 mayperform admission control that may allow at most N users that may bescheduled at a given time. In this embodiment, N may represent thenumber of sub-channels that may be available, and the correspondingnumber of PPUs in OFDMA scheduling device 300. OFDMA scheduling device300 may have N inputs that may accommodate N users. OFDMA schedulingdevice may support modular operation, for example, adding, deleting, ormodifying sub-channel allocation.

In some embodiments of the invention, a user may request to communicateover a plurality of sub-channels. OFDMA scheduling device 300 mayreplicate the input parameters of a user that may request a plurality ofsub-channels over multiple times, and connect that user to a number ofpairs of PPUs and communication sub-channels.

In an embodiment of the invention, each of users 311, 312, 313, and upto user N 319, may provide a Channel Quality Indicator (CQI) to an OFDMAscheduling device 300. A CQI may be provided by each user for every oneof communication sub-channels 331, 332, 333 and up to communicationsub-channel N, 339. Thus, for example, an arbitrary user i may send CQIsto scheduling device 300 for each of N sub-channels, represented byw_(i1) for sub-channel 1, w_(i2) for sub-channel 2, and up to w_(iN) forsub-channel N. Each user up to N users may produce the CQI parametersfor up to N sub-channels. There may be a total of up to N×N CQIparameters for the system, one parameter for each of the potentialuser-sub-channel connections represented by lines 340. The CQI for eachsub-chaninel may be provided to the scheduling device 300, which maysend the CQI parameters to the PPUs associated with each sub-channel.For example, PPU 322 may receive CQI parameter w₁₂ relating to thequality of connection of user 311 over sub-channel 332, CQI parameterw₂₂ relating to the quality of connection of user 322 over sub-channel332, and up to CQI parameter w_(N2) relating to the quality ofconnection of user 319 over sub-channel 332. In some embodiments of theinvention, there may be less than N users. OFDMA scheduling device 300may add null users to increase the total number of users, including bothactual and null users, to N. A null user number of users, including bothactual and null users, to N. A null user may provide a zero CQI input.

It will be understood that in this context, a user may be a device, forexample, a mobile unit connected to a base station or access point. TheCQI may be a dedicated parameter transmitted to the scheduling device300, or it may be derived by the scheduling device 300 from a parameterincluded in the transmission protocol. It will be further understoodthat the channel quality indicator may be a direct measurement of thequality of the sub-channel, for example, a received signal strengthindicator (RSSI), or a substitute or consequential indicator ofsub-channel quality, for example, an error rate or lost packet counter.

FIG. 4 is a schematic block diagram illustrating a PPU 400 according toan embodiment of the present invention and some of its connections.Although the invention is not limited in this respect, and any number ofPPUs N may be used that may correspond to N sub-channels that may be inaccordance with any OFDMA communication protocol, FIG. 4 illustrates byway of example a PPU i 400 in greater detail and connections to otherPPUs 410, 420 and up to PPU N, 490. PPU 400 may receive signals fromother PPUs, for example, communication signal d₁ may be received fromPPU 410, and may be combined in PPU 400 with a CQI w_(1i), where irepresents the serial number of the PPU, and CQI w_(1i) may represent aparameter correlating to the sub-channel quality for user 1 oversub-channel i. Likewise, communication signal d₂ may be received fromPPU 420 and may be combined in PPU 400 with a CQI w_(2i), where CQIw_(2i) may represent a parameter correlating to the sub-channel qualityfor user 2 over sub-channel i, and so on. PPU 400 may receivecommunication signal dN from PPU N 490 and may combine d_(N) with a CQIw_(Ni), where CQI w_(Ni) may represent a parameter correlating to thesub-channel quality for user N over sub-channel i. The CQI parameters wand PPU output signals d may be combined using any suitable combiner,for example, using an adder, multiplier, or other combining circuit. Theoutput of each combination unit may be a path weight for theuser-sub-channel pair.

Calculation unit 405 may perform various calculations using all or someof the combined outputs of the combination units 1 to N. In anembodiment of the invention, calculation unit 405 may calculate amaximum path weight among the combined path weights. weights. The outputof calculation unit 405 may be combined with a CQI w_(ii) by anothercombination circuit, where CQI w_(ii) may represent a parametercorrelating to the sub-channel quality for user i over sub-channel i.PPU 400 may provide an output from distribution unit 498 to each of theother PPUs 410, 420 and up to PPU N 490. It will be understood that eachof PPUs may operate substantially similarly to PPU 400. It will be notedthat other configurations for OFDMA scheduling device 400 are possibleand within the scope of the invention.

An embodiment of the invention may, for example, be used to allocatesub-channels to users, and may have values assigned to CQIs that maycorrespond to combinations of sub-channels and users.

Thus, to take an example, CQIs for a set of N sub-channels and N userswhere N is 4 may be as in the following table:

U1 U2 U3 U4 C1 2 4 3 1 C2 3 1 4 2 C3 4 2 1 3 C4 1 3 2 4

In this example, C1 through C4 may represent sub-channels 1 through 4,respectively, and U1 through U4 may represent users 1 through 4,respectively. A number 1 through 4 in the table may represent a CQI of auser that may operate on a sub-channel. For example, a CQI w₂₃ may havea value of 2, and may represent an indication of a signal quality ofuser U2 operating on sub-channel C3. A higher CQI may, for example,represent an improved quality of a user and sub-channel match.

A parallel processing unit, PPU0, may be developed by a system centralprocessor for a purpose of establishing a connection architecture, andthen may be removed from a resulting architecture. A parallel processingunit PPU0 may be a virtual parallel processing unit, and may haveproperties and features enabling it to operate in a similar fashion asan actual parallel processing unit 400. A parallel processing unit PPU0may be used by a system central used by a system central processorduring an initial assignment of PPUs to sub-channels and may aide indetermining CQIs, as in the table of the example, which may berepresentative of a match between each user and sub-channel. A parallelprocessing unit PPU0 may be used in conjunction with other processingunits. In some embodiments, an initial assignment of parallel processingunits, users and sub-channels that may be based on CQIs, and may bedeveloped by using a parallel processing unit PPU0, may be in accordancewith a construction of a bipartite graph.

For example, PPU0 may be initially assigned to a first user and PPU1 maybe initially assigned to a first sub-channel, w₁₁ may be determined tobe 2, and a best match may be U1 to C1. A second sub-channel and asecond user may be added by initially assigning PPU0 to a second userand PPU2 to a second sub-channel, w₂₁ may be found to be 4, w₁₂ may befound to be 3 and w₂₂ may be found to be 1, and a best match may be U1to C2 and U2 to C1. This process may continue to use PPU0 to determinew_(ij), and then construct a best match from a result. Following a bestmatch allocation PPU0 may be removed from an allocation.

A distribution unit 498 that may be part of PPU 400 may function tocompute a best match in accordance with an embodiment of the invention.In some embodiments, each distribution unit 498 may operate inconjunction with a system central processor. During intermediatecomputations or graph constructions distribution 498 may output resultsto PPUs 410, 420 and up to PPU N 490. Following user and sub-channelallocations, distribution unit 498 may provide a result 495 to a centralsystem processing unit for user and sub-channel assignment. A result maybe found following a convergence of a matching method, where aconvergence of a method may be a result of a finite number of users andsub-channels. A finite number of users and sub-channels may allow for arelative comparison of matches, that may be based on CQIs or otherindicators, of all possible combinations. In some embodiments, abipartite graph may be used as an efficient way of a relative comparisonof matches.

FIG. 5 is a flowchart 500 illustrating a method in accordance withembodiments of the present invention that may be used to allocate users.At block 510 a user may request a sub-channel allocation in order toallow the user to communicate using an OFDMA protocol. At block 520, itmay be determined, for example, by an OFDMA scheduling device, whetherscheduling device, whether the total number of users requesting accessto the system is the same as the number of sub-channels available in theOFDMA system. If the number of users is the same as the number ofsub-channels, the method may proceed to block 560, where optimization ofsub-channel assignments to each of the users may be performed. If thenumber of users requesting access to the OFDMA system is not equal tothe number of sub-channels available, it may be determined at block 530whether the number of users is greater than or less than the number ofsub-channels available. When the number of users is greater than thenumber of sub-channels available, admission control may be performed atblock 550 and the number of users may be limited. When the number ofusers is less than the number of sub-channels available, null users maybe added at block 540 to any unallocated sub-channel. Followingadmission control at block 550 or addition of null users at block 540,optimization of sub-channel assignments to each of the users may beperformed at block 560. Alterations or permutations such asmodifications, additions, or omissions may be made to the method withoutdeparting from the scope of the invention. The method may include more,fewer, or other steps.

FIG. 6 is a flowchart 600 illustrating a method that may be used toperform an optimization of sub-channel assignments in an OFDMA system inaccordance with embodiments of the present invention. Generally, themethod may create a graph by first a first user and sub-channel, andadding further users and sub-channels, and repeating. In someembodiments of the invention, flowchart 600 may be at least partiallyincluded or used in conjunction with, for example, block 560 of FIG. 5.At block 610, information from a first user u₁ and information from afirst sub-channel v₁ may be used to calculate a first graph that may bea two-node bipartite graph G, where a first matching M may be an onlyedge in G, G: M=E(G). A second user u_(i) and a second sub-channel v₁may be added to a first graph at block 620 by adding to each side of G,and the addition to G may be completed by adding edges.

At block 630, a second graph G, which may be referred to as an alternategraph, may be calculated using a first graph G and a first matching M.At block 640, a maximum weight path P, which may be from a second useru_(i) to a second sub-channel v_(i), may calculated, and P may be withinG.

At block 650, a second matching that may be referred to as a maximumweight bipartite matching (MWBM) may be calculated from a maximum weightpath P, (M-M_(p)) ∪M′_(p), where M_(p) and M′_(p) may correspond tovertices and edges of P, respectively.

At block 660 a MWBM may be stored and used in additional calculations ata later time.

At block 670, it may be determined whether all users have been assignedto corresponding sub-channels, and the method may repeat from block 620to add additional users to additional sub-channels until all users havebeen assigned to corresponding sub-channels. Alterations or permutationssuch as modifications, additions, or omissions may be made to the methodwithout departing from the scope of the invention. The method mayinclude more, fewer, or other steps.

FIG. 7 is an exemplary block diagram 700 according to an embodiment ofthe invention illustrating a bipartite alternate graph. Block 710illustrates, for example, a matching that may be between a user 1 and asub-channel c, block 720 illustrates a matching that may be between auser 2 and a sub-channel a, block 730 illustrates a matching that may bebetween a user 3 and a sub-channel b and block 740 illustrates amatching that may be between a user 4 and a sub-channel d. Although theinvention is not limited in this respect, and any number of users may beused that may correspond to N sub-channels that may be in accordancewith any OFDMA communication protocol. Block diagram 700 illustratesconnections that may be formed from the construction and calculation ofa bipartite alternate graph.

In an embodiment of the invention, a matching M may be on a graph G,where M may be a subset of the edges of G, and each vertex in G mayconnect to no more than one edge in M. A bipartite graph may contain twosets of vertices that may be disjoint, and the vertices that may be in afirst set may be connected to vertices in a second set by direct edges.A matching that may be on a bipartite graph may be called a bipartitematching. For example, FIG. 2A may illustrate a bipartite graph 200 andFIG. 2B may illustrate a bipartite matching 250 that may correspond tobipartite graph 200. A path P={v₀e₀v₁e_(l). . . e_(n-1)v_(n)} may bedefined within a graph and may be a finite sequence of alternatingvertices and edges, and may begin and end and edges, and may begin andend with a vertex. Every vertex v_(i) may be directly connected to avertex v_(i+1) by an edge e_(i). A simple path may be a path where eachvertex may be included once. A circle may be a case of a simple paththat may have v_(o) 32 v_(n).

In an embodiment of the invention, G may be formed as a function of afirst set of 1 through n nodes, or left nodes, that may be referred toas U, a second set of n+1 through 2n nodes, or right nodes, that may bereferred to as V, and a set of directed edges of G, that may be referredto as E, and G may be G(U,V,E). E may be defined as: E={e_(ij)|i εU, jεV}. Matching pairs M may consist of a set of elements as M={(a₁,b₁), .. . , (a_(k),b_(k))}. An alternate graph Gmay be constructed where anode i that may be in Gmay correspond to a matching pair {a_(i),b_(i)}in a matching M. A weight of each edge may be defined as w_(ij)=w(a_(i),b_(j)) and w _(ji)=w(b_(i),a_(j)). A cost function, c, mayalso be defined as c_(i)=−w(a_(i),b_(i)) FIG. 7 may represent analternate graph G 700 that may have been constructed from a bipartitegraph G 250, referring also to FIG. 2 b.

In an embodiment of the invention, alternate graph Gmay be constructedfrom a bipartite graph G and a matching M of G. A simple path P that maybe in Gmay correspond to a matching M that may be in G. A weight of Pmay be a difference between a weight of a second matching M′_(p) and afirst matching M_(p). M_(p) may be a matching that may correspond tovertices in P. P may be a simple path, and P={v₀e₀v₁e₁. . .e_(n−1)v_(n)}. Gmay be constructed, and v₀,v₁, . . . ,v_(n) maycorrespond to one or more matching pairs M_(p), where

M _(p){(a _(p) ₀ ,b _(p) ₀ ), . . . (a _(p) _(n) ,b _(p) _(n) )}⊂M,

and where e₀,e₁, . . . ,e_(n−1) may correspond to edges, as {e(a_(p) ₀,b_(p) ₁ ) , . . . e(a_(p) _(n−1) ,b_(p) _(n) )}=M . Each of thevertices in P may be unique, and M′ may be a matching in G, and may havepairs M_(p)={(a_(p) ₀ ,b_(P) ₁ ), . . . (a_(p) _(n−1) ,b_(p) _(n) )}⊂M.A weight of P, W_(p), may be calculated by:

$W_{P} = {{\sum\limits_{i = 0}^{n - 1}w_{v_{i},v_{i + 1}}} + {\sum\limits_{i = 0}^{n - 1}{c_{v_{i}}.}}}$

A weight of matching pairs, W_(MP), may correspond to composite nodesthat may be in path P, and

$W_{M_{P}} = {- {\sum\limits_{i = 0}^{n - 1}{c_{v_{i}}.}}}$

A second matching may be M′, and a weight of a second matching, W_(M)′,may be

$W_{M^{\prime}} = {\sum\limits_{i = 0}^{n - 1}{w_{v_{i},v_{i + 1}}.}}$

A path weight, W_(p), may be a difference of a weight of a firstmatching weight, W_(MP), and a second matching weight, W_(M′),W_(p)=W_(M′)−W_(M) _(p) .

In an embodiment of the invention, C may be a circle in G, andC={v₀e₀v₁e₁. . . e_(n−1)v_(n) e_(n)v₀}. A matching M_(C) may correspondto vertices {v₀. . . v_(n)}, and a matching M_(C′)may correspond toedges {e₀. . . e_(n)}, and (M−M_(C)) ∪M′_(C) may also be a matching inG. C may be a circle, and a first matching M_(C) and a second matchingM_(C′)may contain a common set of vertices. A third matching M _(C) mayalso be a matching, and MC=M−M_(C). M _(C) and M_(C) may have disjointvertices and MC and M′_(C) may have disjoint vertices. A matching mayalso be MC∪M′_(C).

In an embodiment of the invention, M may be a MWBM, and may have size n,and be of a bipartite graph that may have 2n nodes, and may have aweight W_(M). Alternate graph G may be constructed from G and M. Acircle in Gmay have a weight that is not positive. C may be a circle inG, where C={v₀e₀v₁e₁. . . e_(n−1)v_(n)e_(n)v₀}. M_(C) may be a firstmatching that may correspond to vertices, and may have a weight W_(MC),and M′_(C) may be a second matching, and may have a weight W_(MC′), thatmay correspond to edges. M′may be a third matching, where

M′=(M−M _(C))∪M _(C),

and M′ may have a size n and may be in G. A weight of M′, W_(M′), may be

W _(M′) =W _(M) −W _(M) _(C) +W _(m′) _(C)

and a weight of a circle, W_(C), may be

W _(C) −W _(m′) _(C) −W _(M) _(C) =W _(M′) −W _(M)≦0.

G(U,V,E) may be fully connected, may be weighted and may be a bipartitegraph, and may have m nodes, and m may be equal to 2n. G′ may be a graphthat may be constructed from G and an addition of a node to each side ofG, and an addition of edges sufficient to fully connect G′. G′ may be aweighted bipartite graph, G′(U′, V′, E′), and may have m+2 nodes, and

U′=U∪u ₀ ,V′=V∪v ₀ and E′=E∪E ₀ ∪E ₁,

E ₀={(u ₀,ν): ∀νεV′ and E ₁={(u,ν₀):∀u εU′.

G′may be an alternate graph of G′, and may be constructed by adding u₀,v₀, E₀ and E₁ to G. A cost that may be of nodes u₀ and v₀ may be zero.

In an embodiment of the invention, P may be a maximum weight path fromu₀ to v₀, and may be in graph G′. M_(p) and M′_(p) may be a first andsecond matching in G, respectively, and may correspond to vertices andedges of P, respectively. A MWBM matching, M′, of G′ may be

M′=(M−M _(p))∪M′ _(p′)M′

may be a matching that may have a size of n+1, and may be in G′. u₀ maybe connected to a first vertex, b_(k) ₁ , and may be in G′, and may bemapped to a combo-node, V_(k) ₁ , that may also be in G′. A secondvertex, a_(k) ₁ , may be connected to a first vertex, b_(k) ₁ and may beof v_(k) ₂ . M′may be a one-on-one mapping of n+1 left nodes to n+1right nodes. A sequence may continue until a vertex a_(k) _(e) may beconnected to v₀. In M′ there may be a subset of matching pairs,{(u₀,b_(k) ₁ ),(a_(k) ₁ ,b_(k) ₂ ), . . . ,(a_(k) _(e−1) ,b_(k) _(e)),(a_(k) _(e) ,v₀)}, that may correspond to a simple path P that may bebetween u₀ and v₀, and may be in G′, and may have vertices that may havea sequence, u₀v_(k) ₁ . . . v_(k) _(e) v₀. M′_(p) and M_(p) may beconstructed from path P. M′_(p) may contain all of the vertices that maybe in M_(p), and may also contain two additional vertices u₀ and v₀. M′may then be a matching that may have a size n+1, and may be in G′, andmay have a weight, W_(M′), and W_(M′)=W_(M)−W_(M) _(p) +W_(M′) _(P)=W_(M)+W_(P). There may be a maximum weight path, P₀, that may notcontain any circle, and M_(p) ₀ and M′_(p) ₀ may be constructed from P₀,and M′₀=(M−M_(P) ₀ )∪M′_(p) ₀ and W_(M′) ₀ =W_(M)+W_(p) ₀ ≧W_(M′). M′₀may be a MWBM and may have a size n+1.

In an embodiment of the invention, a MWBM for m nodes may beconstructed, and may start from two nodes. Each step may include anaddition of a node to each side of a bipartite graph to an existinggraph. An optimal matching of an extended graph may be found bycomputing a maximum weight path that may be between an existing graphand a graph that may have added nodes.

An OFDMA system may have N sub-channels, which may be allocated to Mconcurrent users, and may be in a given frame. Each user may beallocated more than one sub-channel, or some sub-channels may not beallocated to any user. Virtual nodes may be created, and if a user mayneed m sub-channels, a user may be mapped to m virtual nodes. Null usersmay have zero weight and may be added as necessary. Following creationof virtual nodes, as necessary, an allocation may be performed as inexemplary FIG. 5.

In an embodiment of the invention, a MWBM, M, may be a first matching,and may be of a first graph, G. A matching pair (u_(i), v_(j)) may beremoved from M and G, and a second matching, M′, may be formed, where M′may be a MWBM and may be in a second graph, G+. This MWBM allocation mayallow a user to be added, deleted or modified. A deletion may beaccomplished by removing a node node u_(i) and as matching sub-channelv_(i) from M and G, and a result may be M′ and G′. A null node and asub-channel v_(i) may be added to G′, and a corresponding MWBM may befound. A node may be added when a null node may be in an existingallocation. A null node may be removed with a corresponding sub-channel,and a new node may be added, and the corresponding sub-channel may bereturned. A node may be modified by removing a node and a correspondingsub-channel, modifying a node, and returning a node and a correspondingsub-channel that may have modified weights.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intendedintended to cover all such modifications and changes as fall within thespirit of the invention.

1. A method comprising: receiving from a plurality of users respectiverequests for allocation of orthogonal frequency division multiple.access(OFDMA) sub-channels; obtaining a channel quality index for each of saidusers over each sub-channel of the OFDMA system; calculating anoptimization of sub-channels based on said channel quality indices; andallocating said plurality of OFDMA sub-channels to said plurality ofusers based on said optimization.
 2. The method of claim 1, furthercomprising communicating with each of said users over said allocatedsub-channel.
 3. The method of claim 1, wherein calculating anoptimization of sub-channels based on said channel quality indicescomprises: for each sub-channel performing the following: calculating aplurality of path weights based on channel quality index values forusers to said sub-channel and based on path weight outputs of othersub-channels; selecting a maximum path weight of said plurality of pathweights; and combining said maximum path weight with the channel qualityindex for the sub-channel.
 4. The method of claim 1, wherein saidplurality of users include first and second users, and whereincalculating said optimization comprises: calculating a first graphincluding at least two nodes, wherein said first node calculated fromsaid first user and said second node calculated from a firstsub-channel; calculating a first edge of said first graph from a firstmatching calculated from said first and second nodes; adding to saidfirst graph a third node calculated from said second user and a fourthnode calculated from a second sub-channel; calculating a second edgefrom a second matching calculated from said third and fourth nodes;calculating a second graph based at least on said first graph, saidsecond edge, said third node, and said fourth node; calculating amaximum weight path from said third node to said fourth node within saidsecond graph, and wherein allocating said plurality of OFDMAsub-channels to said first and second users comprises allocating saidsub-channels based on said maximum weight path.
 5. The method of claim4, wherein said first graph and said second graph are bipartite graphs.6. The method of claim 4, further comprising storing said first graphand said second graph in a memory.
 7. The method of claim 1, whereinsaid OFDMA system is a wireless network system.
 8. The method of claim1, wherein said allocation further comprises allocation of two or moresub-channels to each of one or more of said users, based on admissioncontrol requests of said users.
 9. The method of claim 1, wherein saidallocation further comprises allocation of one or more sub-channels toone or more null users, based on said optimization.
 10. The method ofclaim 4, wherein calculation of said optimization further comprises:subtracting said third node and said fourth node from said second graph;modifying said third node; adding modified third node and said fourthnode to said second graph; calculating a third matching from saidmodified third node and said fourth nodes; calculating a third edge fromsaid third matching; calculating a third graph from said second graph,said third edge, said modified third node and said fourth node; andcalculating a maximum weight path from said modified third node to saidfourth node within said third graph.
 11. A system comprising: aplurality of mobile units adapted to transmit a channel quality indexrelating to quality of communication for the mobile unit over eachsub-channel; and a wireless server adapted to communicate with saidmobile units using OFDMA protocol, said wireless server comprising: aplurality of processing units, each adapted to communicate data over arespective sub-channel, wherein each of said plurality of processingunits is connected to receive an output of every other of saidprocessing units, and an allocation unit to calculate optimal allocationof sub-channels to users based on said channel quality indices receivedfrom said mobile units.
 12. The system of claim 11, further comprising atransmitter connected to said server to communicate with each of saidusers over said allocated sub-channel.
 13. The system of claim 11,wherein said allocation unit is to calculate said optimal allocation ofsub-channels based on said channel quality indices by: for eachsub-channel perforrming the following: calculating a plurality of pathweights based on channel quality index values for users to saidsub-channel and based on path weight outputs of other sub-channels;selecting a maximum path weight of said plurality of path weights; andcombining said maximum path weight with the channel quality index forthe sub-channel.
 14. The system of claim 11, wherein said plurality ofusers include first and second users, and wherein calculating saidoptimal allocation comprises: calculating a first graph including atleast two nodes, wherein said first node calculated from said firstuser-and said second node calculated from a first sub-channel;calculating a first edge of said first graph from a first matchingcalculated from said first and second nodes; adding to said first grapha third node calculated from said second user and a fourth nodecalculated from a second sub-channel; calculating a second edge from asecond matching calculated from said third and fourth nodes; calculatinga second graph based at least on said first graph, said second edge,said third node, and said fourth node; calculating a maximum weight pathfrom said third node to said fourth node within said second graph, andwherein allocating said plurality of OFDMA sub-channels to said firstand second users comprises allocating said sub-channels based on saidmaximum weight path.
 15. The system of claim 14, wherein said firstgraph and said second graph are bipartite graphs.
 16. The system ofclaim 14, wherein said server further comprises a memory to store saidfirst graph and said second graph.
 17. The system of claim 11, whereinsaid allocation unit is to calculate optimal allocation by allocation oftwo or more sub-channels to each of one or more of said users, based onadmission control requests of said users.
 18. The system of claim 11,wherein said allocation unit is to calculate optimal allocation byallocation of one or more sub-channels to one or more null users basedon said optimization.
 19. The system of claim 14, wherein saidallocation unit is to calculate optimal allocation by: subtracting saidthird node and said fourth node from said second graph; modifying saidthird node; adding modified third node and said fourth node to saidsecond graph; calculating a third matching from said modified third nodeand said fourth nodes; calculating a third edge from said thirdmatching; calculating a third graph from said second graph, said thirdedge, said modified third node and said fourth node; and calculating amaximum weight path from said modified third node to said fourth nodewithin said third graph.
 20. The system of claim 19, wherein said thirdnode is a calculated from a null user.